Overview

Brief Summary

Southern magnolia (Magnolia grandiflora), also called evergreen magnolia, bull-bay, big-laurel, or large-flower magnolia, has large fragrant white flowers and evergreen leaves that make it one of the most splendid of forest trees and a very popular ornamental that has been planted around the world. This moderately fast-growing medium-sized tree grows best on rich, moist, well-drained soils of the bottoms and low uplands of the Coastal Plains of Southeastern United States. It grows with other hardwoods and is marketed as magnolia lumber along with other magnolia species to make furniture, pallets, and veneer. Wildlife eat the seeds, and florists prize the leathery foliage.

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There are about 225 species in the magnolia family. This is one of the oldest families of flowering plants. It appeared before bees did, so almost all species are pollinated by beetles. The southern magnolia has leathery leaves and large, white flowers that smell lemony. This tree is planted in gardens. It is also used to make furniture.

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Comprehensive Description

Description

Southern magnolia is a medium, evergreen tree that grows to about 50 ft (15 m) with a straight trunk and conical crown. It does not get extremely large in most of its range, but can occasionally grow to 100 ft (30 m). Leaves: The leaves are distinctly alternate. Southern magnolias have a dense growth of smooth, leathery evergreen leaves that are 5 to 10 in (12 to 24 cm) long, dark, shiny green on top, and rusty below. Flowers: Fragrant, creamy-white flowers (which discolor easily if bruised), appear on the ends of thick, tough stems all over the tree. They are cup-shaped, about 8 in across, with 6 thick petals, wider at the tip. The blossoms open at about 9:00 a.m. and close at night for 2 or 3 days; then all the stamens are shed and the flower reopens, turns brown, and disintegrates. Flowering occurs in the spring. The flowers appear throughout the summer and into the fall. Fruits: Conelike seedpods contain large red seeds. When the pods open, the seeds often fall from place and hang by silky threads. Bark: The bark is gray, rough, thick, and furrowed in thick plates. The twigs are densely red or white and hairy. Habitat: Southern magnolia can be found throughout the southern coastal plain from the Carolinas to eastern Texas and thrives in wooded dunes, hammocks, river bottoms, ravine slopes, and coastal plains. It is also commonly planted in parks and along streets in areas of mild climate across the country.

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Distribution

Range Description

Magnolia grandifloraoccurs in the southeastern United States of America. Its range extends from eastern North Carolina, south along the Atlantic Coast to the Peace River in central Florida, then westward through the southern half of Georgia, Alabama and Mississippi and across Louisiana into southeast Texas. Throughout its natural range it occurs at elevations between 60 and 150 m asl. Coastal areas within its range are all less than 30 m asl. In the northern part of its range in Mississipi it is found at elevations of 90 to 120 m asl.

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The range of southern magnolia extends from North Carolina along theAtlantic Coast to central Florida, westward through the southern half ofGeorgia, Alabama, and Mississippi, and across Louisiana into easternTexas [2,24]. It is cultivated in Hawaii [32].

2. Bray, William L. 1901. The ecological relations of the vegetation of western Texas. Botanical Gazette. 32: 99-123. [4447]

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The range of southern magnolia extends from eastern North Carolina, south along the Atlantic Coast to the Peace River in central Florida, then westward through roughly the southern half of Georgia, Alabama, and Mississippi, and across Louisiana into southeast Texas. It is most prevalent in Louisiana, Mississippi, and Texas (12,14).

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Description

Southern magnolia is a fast-growing, medium-sized, native evergreen treethat grows 60 to 90 feet (18-27 m) tall [9,12]. The large, whiteflowers are perfect and fragrant. The seeds are drupelike with a soft,fleshy outer seed coat and an inner stony portion. Southern magnoliadevelops a deep taproot. As trees grow the root structure changes.Trees of sapling stage and beyond have a rather extensive root system.Older trees develop a fluted base with the ridges corresponding to theattachment of major lateral roots [5,12].

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Ecology

Habitat

Habitat and Ecology

Magnolia grandifloraproduces large fragrant white flowers and evergreen leaves that make it one of the most splendid forest trees. It is a moderately fast growing medium sized tree which grows best on rich, loamy moist and well drained soils of the bottoms and low uplands of the Coastal Plains of Southeastern United States, along streams and near swamps. It also grows on mesic upland sites where fire is rare. It grows in warm temperate to subtropical climates where the temperatures rarely fall lower than -9 °C or above 38 °C. Although primarily a bottomland species it cannot withstand prolonged inundation and thus grows mostly on the oldest alluvium and outwash sites.Magnolia grandiflorararely exists alone and is associated with a variety of mesic hardwoods consisting of species such as Oak, Pine, Swamp Chestnut and Beech. It produces large white flowers between April and June and fleshy cone like fruit matures from September through the late fall. Southern magnolia is a prolific seed producer and good seed crops normally occur every year. Trees as young as 10 years old can produce seeds and optimum seed production occurs at 25 years of age. The relatively heavy seeds are dispersed by birds and mammals but some may be spread by heavy rains. Seedlings are very susceptible to frost damage and even a light freeze can cause mortality.

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Climate

Southern magnolia grows in warm temperate to semitropical climates (2). The frost-free period is at least 210 days and is more than 240 days for much of the range. Average January temperatures along the coast are 9° to 12° C (49° to 54° F) in South Carolina and Georgia and 11° to 21° C (52° to 70° F) in Florida. Coastal temperatures average 27° C (80° F) during July. Temperatures below -9° C (15° F) or above 38° C (100° F) are rare within the species natural range.

Annual rainfall averages 1020 to 1270 mm (40 to 50 in) in the northeastern portion of the range and 1270 to 1520 mm (50 to 60 in) in other areas. A small area along the Gulf Coast receives 1520 to 2030 mm (60 to 80 in) yearly. In the Atlantic Coastal Plain, summer is usually wettest and autumn driest. Periodic summer droughts occur in the western part of the range.

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General Ecology

Fire Management Considerations

Where fire is surpressed or infrequent, southern magnolia and live oakcan become dominant species in the southern mixed hardwood forests. Thetransition from an open, fire-dominated forest to a closed-canopy,deciduous forest favors the Quercus-Magnolia climax community [3,6,10].

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Successional Status

Southern magnolia is moderately tolerant of shade. It can endureconsiderable shade in early life but needs more light as it becomesolder [13]. Southern magnolia will invade pine or hardwood stands andis able to reproduce under a closed canopy. It will not reproduce underits own shade. Once established, it can maintain or increase itspresence in stands by sprouts and seedlings that grow up throughopenings, which occur sporadically in the canopy [24]. Southernmagnolia has been migrating onto mesic upland sites and establishingitself, along with associated hardwoods, as part of the climax forest[22,23].

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Regeneration Processes

Southern magnolia is a prolific seed producer, and good seed cropsusually are produced every year. Trees as young as 10 years can produceseed, but optimum seed production does not occur until age 25. Cleanedseeds range from 5,800 to 6,800/pound (12,800-15,000/kg). Seedviability averages about 50 percent. The relatively heavy seeds aredisseminated by birds and mammals, but some may be spread by heavy rains[24]. Southern magnolia is pollinated by insects [23,30].

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Reaction to Competition

Overall, southern magnolia is tolerant of shade. It can endure considerable shade in early life (8), but needs more light as it becomes older (2). It will invade existing stands and is able to reproduce under a closed canopy (3,8). Once established, it can maintain or increase its presence in stands by sprout and seedling production that grows up through openings, which occur sporadically in the canopy.

Southern magnolia is considered to be one of the major species of the potential climax forest of the southeastern Coastal Plains (3,6,15,16,20). In the past, regular burning restricted the species to the wetter sites, as seedlings are easily killed by fire. Older trees, however, due to bark characteristics, are quite fire resistant (3,10) and even if the tops are killed, they sprout vigorously. Since the advent of improved fire control, southern magnolia has been migrating onto mesic upland sites and establishing itself, along with associated hardwoods, as part of the climax forest.

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Rooting Habit

Southern Magnolia is a deep-rooted species, except on sites with a high water table. Seedlings quickly develop one major taproot. As trees grow the root structure changes. Trees of sapling stage and beyond have a rather extensive heart root system (i.e. several to many sunken roots grow down from the root collar of the tree trunk). Older trees may develop a fluted base with the ridges corresponding to the attachment of major lateral roots.

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Reproduction

Vegetative Reproduction

Mature southern magnolia commonly develops root and stump sprouts (3). Portions of lower limbs of saplings often become imbedded in the forest floor where they develop roots, eventually producing separate trees. Air-layering, stem cuttings, and grafts have all been used to propagate the species for ornamental plantings.

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Seedling Development

Seeds usually germinate the first or second spring following seedfall Germination is epigeal (19). The best natural seedbed is a rich, moist soil protected by litter. Even though viable, seeds rarely germinate under the parent tree because of reported inhibitory effects (3).

Seedlings are very susceptible to frost damage, and even a light freeze can cause mortality. Partial shade is beneficial for the first 2 years of seedling growth. Under favorable conditions growth is quite rapid. In nurseries, seedlings usually grow 46 to 61 cm (18 to 24 in) the first year (2).

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Seed Production and Dissemination

The seeds are drupelike, with a soft, fleshy outer seedcoat and an inner stony portion. Southern magnolia is a prolific seed producer and good seed crops normally occur every year (14). Trees as young as 10 years old can produce seed, but optimum seed production under forest conditions usually does not occur until age 25. Cleaned seeds range in number from 12,800 to 15,000/kg (5,800 to 6,800/lb) and average 14,200/kg (6,450/lb) (19). Seed viability averages about 50 percent. The relatively heavy seeds are disseminated mostly by birds and mammals, but some may be spread by heavy rains.

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Flowering and Fruiting

The large, white, fragrant flowers are perfect (19) and appear from April to June. The fleshy conelike fruit matures from September through the late fall. When the fruit matures and opens, seeds 6 to 13 mm (0.25 to 0.5 in) long emerge and hang temporarily suspended by slender, silken threads before dropping (2).

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Growth

Growth and Yield

On good sites, southern magnolia trees average 18 to 24 in (60 to 80 ft) tall and 61 to 91 cm (24 to 36 in) in d.b.h. in 80 to 120 years. Heights of 30 to 38 in (100 to 125 ft) have been reported in Florida (2). Annual diameter growth for large mature trees in an east Texas stand was .24 cm (.09 in) (8). In unmanaged natural stands in the Florida panhandle, trees without overtopping competition will average .76 cm (.3 in) of diameter growth and 0.46 m (1.5 ft) of height growth per year through age 50. Under natural conditions, many trees spend 10 to 20 years in the understory before they reach the upper canopy. Annual diameter growth for these trees is .51 cm (.2 in) and average height growth is .31 m (1.0 ft) to age 50 years.

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Molecular Biology and Genetics

Genetics

No work has been done to characterize individual populations. Extensive breeding has been done to develop races of southern magnolia for ornamenta use (13). Common varieties include Magnolia grandiflora lanceolata with a narrow pyramidal habit and M. grandiflora gallissoniensis, reported to be cold hardy (17).

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Trends

Population

Magnolia grandiflorais abundant throughout its range. It is most prevalent in Louisiana, Mississippi and Texas. Air-layering, stem cuttings and grafts have all been used to propagate this species for ornamental plantings.

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Threats

In the past regular burning restricted the species to the wetter sites as seedlings are easily killed by fire. Young trees are susceptible to fire-caused injury and mortality.Older trees, due to their bark characteristics, are quite fire resistant and even if the tops are burned can resprout. Since the advent of improved fire control this species has migrated onto mesic upland sites and established itself along with associated hardwoods as part of the climax forest. Winter droughts can cause extensive dieback and mortality. A leaf spot caused by the fungus Mycosphaerella millerican be a problem to nursery seedlings.

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Management considerations

Winter drought can cause extensive dieback and mortality of southernmagnolia. Seedlings are susceptible to frost damage; even a lightfreeze can cause mortality. A number of Fomes and Polyporus fungi causeheartrot in southern magnolia. Heavy infestations of magnolia scale(Neolecanium cornuparyum) kill branches or entire trees [14,24].

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Relevance to Humans and Ecosystems

Benefits

Other uses and values

Southern magnolia is a valuable and extensively planted ornamental. Theleaves, fruit, bark, and wood yield a variety of extracts with potentialapplications as pharmaceuticals [14,24]. Southern magnolia is a goodurban landscape tree because it is resistant to acid deposition [24].

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Special Uses

Because of its showy flowers and lustrous evergreen foliage, southern magnolia is a valuable and extensively planted ornamental. In many urban areas where other species do poorly, this magnolia can grow because of its resistance to damage by sulfur dioxide. The seeds are eaten by squirrels, opossums, quail, and turkey (9). The leaves, fruits, bark and wood yield a variety of extracts with potential applications as pharmaceuticals (4,5).

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Wikipedia

Magnolia grandiflora

Magnolia grandiflora, commonly known as the southern magnolia or bull bay, is a tree of the family Magnoliaceae native to the southeastern United States, from Virginia south to central Florida, and west to East Texas and Oklahoma. Reaching 27.5 m (90 ft) in height, it is a large, striking, evergreen tree with large, dark green leaves up to 20 cm (8 in) long and 12 cm (4.5 in) wide, and large, white, fragrant flowers up to 30 cm (12 in) in diameter. Widely cultivated in warmer areas around the world, over 50 cultivars have been bred and marketed commercially. The timber is hard and heavy, and has been used commercially to make furniture, pallets, and veneer.

Magnolia grandiflora is a medium to large evergreen tree which may grow 120 ft (36.5 m) tall.[1] It typically has a single stem (or trunk) and a pyramidal shape.[2] The leaves are simple and broadly ovate, 12–20 cm (5–8 in) long and 6–12 cm (2–5 in) broad,[2] with smooth margins. They are dark green, stiff and leathery, and often scurfy underneath with yellow-brown pubescence. The large, showy, lemoncitronella-scented flowers are white, up to 30 cm (12 in) across and fragrant, with six to 12 petals with a waxy texture, emerging from the tips of twigs on mature trees in late spring. Flowering is followed by the rose-coloured fruit, ovoid, 7.5–10 cm (3–4 in) long, and 3–5 cm (1.5–2 in) wide.[3]

Exceptionally large trees have been reported in the far southern United States. The national champion is a specimen in Smith County, Mississippi, that stands an incredible 37 m (122 feet). Another record includes a 35-m-high specimen from the Chickasawhay District, De Soto National Forest, in Mississippi, which measured 17.75 ft in circumference at breast height, from 1961, and a 30-m-tall tree from Baton Rouge, which reached 18 ft in circumference at breast height.[3]

Magnolia grandiflora was one of the many species first described by Linnaeus in his Systema Naturae in 1759, basing his description on the earlier notes of Miller. He did not select a type specimen. Its specific epithet is derived from the Latin words grandis "big", and flor- "flower".[4]

M. grandiflora is most commonly known as southern magnolia, a name derived from its range in the Southern United States. Many broadleaved evergreen trees are known as bays for their resemblance to the leaves of the red bay (Persea borbonia), with this species known as the bull bay for its huge size or alternatively because cattle have been reported eating its leaves. Laurel magnolia,[4] evergreen magnolia,[3] large-flower magnolia or big laurel are alternative names.[5] The timber is known simply as magnolia.[3]

Southern magnolias are native to the Southeastern United States, from southeast Virginia south to central Florida, and then west to East Texas and Oklahoma. It is found on the edges of bodies of water and swamps, in association with sweetgum (Liquidambar styraciflua), water oak (Quercus nigra), and black tupelo (Nyssa sylvatica). In more sheltered habitats, it grows as a large tree, but can be a low shrub when found on coastal dunes.[6] It is killed by summer fires, and is missing from habitats that undergo regular burning.[7]

In Florida, it is found in a number of different ecological areas that are typically shady and have well-draining soils; it is also found in hummocks, along ravines, on slopes, and in wooded floodplains.[8] Despite preferring sites with increased moisture, it does not tolerate inundation.[3] It grows on sand-hills in maritime forests, where it is found growing with live oaks and saw palmetto.[7] In the eastern United States, it has become an escape, and has become naturalized in the tidewater area of Virginia and locally in other areas outside of its historically natural range.[9]

M. grandiflora can produce seed by 10 years of age, although peak seed production is achieved closer to 25 years of age. Around 50% of seeds can germinate, and they are spread by birds and mammals.[3] Squirrels, opossums, quail, and turkey are known to eat the seeds.[10]

The plant collector Mark Catesby, the first in North America, brought M. grandiflora to Britain in 1726, where it entered cultivation and overshadowed M. virginiana, which had been collected a few years earlier. It had also come to France, the French having collected it in the vicinity of the Mississippi River in Louisiana.[11] It was glowingly described by Philip Miller in his 1731 work The Gardeners' Dictionary.[12] One of the earliest people to cultivate it in Europe was Sir John Colliton of Exeter in Devon; scaffolding and tubs surrounded his tree, where gardeners propagated its branches by layering, the daughter plants initially selling for five guineas each (but later falling to half a guinea).[12]

It is often planted in university campuses and allowed to grow into a large tree, either with dependent branches, or with the lower branches removed to display the bare trunks. It is also espaliered against walls, which improves its frost-hardiness.[4]

It is a very popular ornamental tree throughout its native range in the coastal plain of the Gulf/South Atlantic states. Grown for its attractive, shiny green leaves and fragrant flowers, it has a long history in the southern United States. Many large and very old specimens found in the subtropical port cities such as New Orleans, Mobile, Savannah, Charleston, and Wilmington, NC. M. grandiflora is the state tree of Mississippi and the state flower of Louisiana.

The species is also cultivated in the warmer parts of the United States; On the East Coast, a small number of specimens can be found growing as far north as coastal areas of New Jersey, Connecticut, and Long Island, NY. Farther south, it is grown more widely in Delaware, much of the Chesapeake Bay region in Maryland, and much of eastern Virginia. On the West Coast, it can be grown as far north as British Columbia/Seattle area, though cooler summers on the West Coast slow growth compared to the East Coast.[4]

In the interior of the US, some of the cold-hardy cultivars have survived north to the southern Ohio Valley (southern Ohio, Kentucky, southern Indiana). Farther north, few known long term specimens are found due to the severe winters, very cold temperatures, and/or lack of sufficient summer heat.

Magnolia grandiflora is also grown in parts of Mexico, Central America, and South America as well as parts of Asia.[4]

It is recommended for seashore plantings in areas that are windy but have little salt spray.[13] The foliage will bronze, blotch, and burn in severe winters at the northern limits of cultivation, especially when grown in full winter sun,[14] but most leaves remain until they are replaced by new foliage in the spring. In climates where the ground freezes, winter sun appears to do more damage than the cold. In the Northern Hemisphere, the south side of the tree will experience more leaf damage than the north side. Two extremes are known, with leaves white underneath and with leaves brown underneath. The brown varieties are claimed to be more cold-hardy than the white varieties, but this does not appear to be proven as yet. Once established, the plants are drought tolerant, and the most drought tolerant of all the Magnolia species.[14]

The leaves are heavy and tend to fall year round from the interior of the crown and form a dense cover over the soil surface,[14] and they have been used in decorative floral arrangements.[15] The leaves have a waxy coating that makes them resistant to damage from salt and air pollution.[14]

In the United States, southern magnolia, along with sweetbay (Magnolia virginiana) and cucumbertree (Magnolia acuminata), is commercially harvested. Lumber from all three species is simply called magnolia, which is used in the construction of furniture, boxes, pallets, venetian blinds, sashes, and doors and used as veneers. Southern magnolia has yellowish-white sapwood and light to dark brown heartwood tinted yellow or green. The usually straight-grained wood has uniform texture with closely spaced rings. The wood is ranked moderate in heaviness, hardness, and stiffness, and moderately low in shrinkage, bending, and compression strength; it is ranked moderately high in shock resistance.[16] Its use in the Southeastern United States has been supplanted by the availability of harder woods.[17]

Over 50 cultivars have been developed and named in North America and Europe. Most plants in nurseries are propagated by cuttings, resulting in more consistent form in the various varieties available.[18] Many older cultivars have been superseded by newer ones and are no longer available.[19] Some cultivars have been found to be more cold hardy, they include:

'Bracken's Brown Beauty', developed by Ray Bracken of Easley, South Carolina, in the late 1960s, is a popular cultivar which has survived long-term in southern Ohio, West Virginia, New Jersey, and Long Island, NY. This cultivar grows in a dense and compact pattern, with narrow, medium-sized, glossy leaves. Flowers measure 5-6 in (12.5 - 15.0 cm).

'Edith Bogue' was brought to the coastal plain of New Jersey from Florida in the 1920s. The original tree sent to Edith A. Bogue from Florida helped to establish cold-hardy specimens in the Middle Atlantic states from Delaware to coastal Connecticut. Once established, 'Edith Bouge' has been known to have only minor spotting and margin burn on the leaf in temperatures as low as -5 °F (-20 °C). With a vigorous classic pyramidal shape, this cultivar grows to 35 ft with a 15-ft spread.

'Angustifolia', developed in France in 1825, has narrow, spear-shaped leaves 20 cm (8 in) long by 11 cm (4.4 in) wide, as its name suggests.[18]

'Exmouth' was developed in the early 18th century by John Colliton in Devon. It is notable for its huge flowers, with up to 20 tepals, and vigorous growth. Erect in habit, it is often planted against walls. The leaves are green above and brownish underneath.[20] The flowers are very fragrant and the leaves are narrow and leathery.[21]

'Goliath' was developed by Caledonia Nurseries of Guernsey, and has a bushier habit and globular flowers of up to 30 cm (12 in) diameter. Long-flowering, it has oval leaves which lack the brownish hair underneath.[20]

'Little Gem', a dwarf cultivar, is grown in more moderate climates, roughly from Maryland and the Virginias southward. Originally developed in 1952 by Steed's Nursery in Candor, North Carolina, it is a slower-growing form with a columnar shape which reaches around 4.25 m (14 ft) high and 1.2 m (4 ft) wide. Flowering heavily over an extended period in warmer climate, it bears medium-sized, cup-shaped flowers, and has elliptic leaves 12.5 cm (5 in) long by 5 cm (2 in) wide.[20]

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Notes

Comments

Magnolia grandiflora (a hexaploid) is highly variable, especially the leaves, which range from glabrous to densely red-brown felted on the abaxial surface. It is the only magnolia species in the flora with free stipules, and the inner spathaceous bract is unique among Magnolia taxa in the flora. Curled filiform trichomes occur on the abaxial leaf surface. In the wild, hybrids with M. virginiana (a diploid) have been reported but not confirmed by the present author. The compatibility of these taxa is well known from the Freeman hybrid, a highly sterile tetraploid growing at the U.S. National Arboretum in Washington, D.C. In crosses using the hexaploid M. grandiflora , this parent is dominant and nearly masks the other parent.

Magnolia grandiflora is an escape, and it naturalizes in the tidewater area of Virginia and locally elsewhere beyond its natural range in the southeastern United States. It ranks among the noblest of North American broadleaved trees and is cultivated widely in the United States and in many other countries. A large number of cultivars have been introduced to horticulture.

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Names and Taxonomy

Taxonomy

The currently accepted scientific name for southern magnolia is Magnoliagrandiflora L. [19]. The genus Magnolia consists of 35 species ofdeciduous or evergreen trees or shrubs in North and Central America,eastern Asia and the Himalayas; nine species are native to the UnitedStates [23].